Infrared and Raman spectra of trithiadiborolanes, SB(X)SB(X)S, with X Cl, Br, I or Ch3†

Infrared and Raman spectra of the above four compounds have been obtained in the liquid and solid states down to 35 cm−1 (infrared) or to about 70 cm−1 (Raman). The results provide good evidence (but not rigorous proof) that the molecules are planar and have C2ν symmetry. The presence of boron isotopes causes splitting of some of the higher frequency bands. Assignments have been made for 57 of the 60 skeletal fundamentals of the 11B–11B isotopic molecules About ⅔ of these are reliable; the remainder are not well established. The S–S stretching frequency is at 449, 436, 425 and 479 cm−1 in the Cl, Br, I and CH3 compounds respectively. The planarity of the rings can be explained on the basis of bond angles alone, or on the postulate of an aromatic ring system. There is at present no other evidence to support the latter. The vibrational spectra provide no evidence about π bonding in these molecules.